TEMPO.CO, Jakarta - Meteorology, Climatology, and Geophysics Agency (BMKG) called on the people to raise vigilance following three earthquakes that had rocked Blora, Central Java this December. The quakes were triggered by Pati Thrust Fault.
The latest quake measured at 3.6 magnitudes occurred on Wednesday, December 25. “Pati thrust fault has the highest possible magnitude of quake up to 6.5 with a fault rate of 0.1 mm per year,” said the BMKG head of earthquake and tsunami mitigation Daryono in Jakarta, Thursday, December 26.
The agency’s analysis results showed the latest tremor's epicenter was at 6.87 degrees south latitude and 111.30 degrees east longitude on land, 16 km northwest of Blora, at a depth of 13 km. Judging from its shallow hypocenter depth, the tremor was caused by active fault activity.
"Since December 18, three quakes had jolted areas of Pati, Lasem, and Blora,” Daryono added.
The first occurred on December 18 with a magnitude of 2.9 at 12:19 p.m., while the second one was recorded on the same day at 8:33 p.m. The epicenters of the three were located right on the Pati thrust fault line.
Daryono mentioned that in 1890, a strong quake with a magnitude of 6.8 hit Pati, Central Java. This shallow tremor caused severe damages with the intensity of VI-VII MMI level, and the radius of damage reaching around 500 km.
"So by taking into account the fact of the active Pati thrust fault and historical records of strong earthquakes that had occurred, we should raise awareness regarding the recent increase in tectonic earthquake activity in Pati, Blora region," Daryono concluded.